Re: [Qemu-devel] [PULL 17/29] target/riscv: Convert quadrant 1 of RVXC insns to decodetree

[Palmer Dabbelt]

On Fri, Mar 15, 2019 at 4:19 AM Palmer Dabbelt <address@hidden> wrote:

> On Fri, 15 Mar 2019 02:06:07 PDT (-0700), Bastian Koppelmann wrote:
> > Hi Alistair
> >
> > On 3/14/19 9:28 PM, Alistair Francis wrote:
> >> On Wed, Mar 13, 2019 at 7:53 AM Palmer Dabbelt <address@hidden>
> wrote:
> >>> From: Bastian Koppelmann <address@hidden>
> >>>
> >>> Reviewed-by: Richard Henderson <address@hidden>
> >>> Signed-off-by: Bastian Koppelmann <address@hidden>
> >>> Signed-off-by: Peer Adelt <address@hidden>
> >> This commit is the first bad commit in breaking 32-bit boot.
> >>
> >> It looks like the jal doesn't jump to the correct address:
> >>
> >> ----------------
> >> IN:
> >> 0x80000022:  00050433          add             s0,a0,zero
> >> 0x80000026:  000584b3          add             s1,a1,zero
> >> 0x8000002a:  2c79              jal             ra,670          #
> 0x800002c8
> >>
> >> ----------------
> >> IN:
> >> 0x800002c8:  00000533          add             a0,zero,zero
> >> 0x800002cc:  8082              ret
> >
> >
> > Oops! Can you point me to the binary to reproduce this?
>
> I think I've traced it down to something simple: in my hello world binary
> I see
>
>     20401a8c:       2a45                    jal     20401c3c <atexit>
>
> in the objdump, and I see
>
>     IN: _start
>     0x20401a8c:  2a45              jal             ra,432          #
> 0x20401c3c
>
> but then QEMU jumps to 0x20401a9d.  I have a feeling it's something wrong
> with
> gen_jal() that disappeared during the cleanups that we dropped in order to
> fix
> the build issues.
>
> I'm running
>
>     ./riscv32-softmmu/qemu-system-riscv32 -machine sifive_e -kernel
> ~/work/sifive/freedom-e-sdk/software/hello/hello -nographic -d
> in_asm,out_asm,exec,cpu -singlestep |& tee out.log
>
> on the "hifive1" branch of github.com/palmer-dabbelt/qemu, which just has
> a
> PRCI fixup that I forgot about and haven't sent upstream yet (I'll do that
> after this issue).  The binary should be at
>
>     http://www.dabbelt.com/~palmer/hello.elf
>
> and the debug log at
>
>     http://www.dabbelt.com/~palmer/out.log
>
> You can build the binary from github.com/sifive/freedom-e-sdk via
>
>    make software PROGRAM=hello TARGET=sifive-hifive1
>
> using the riscv64-unknown-elf-gcc-20181127-x86_64-linux-ubuntu14 toolchain
> binaries from our website (newer ones should work, but probably won't
> produce
> exactly the same output).
>
> I'll poke around after grabbing some dinner...
>

OK, I'm pretty sure this is it:

c_jal_addiw       001 .  .....  ..... 01 @ci #Note: parse rd and/or imm
manually

static bool trans_c_jal_addiw(DisasContext *ctx, arg_c_jal_addiw *a)
{
#ifdef TARGET_RISCV32
    /* C.JAL */
    arg_jal arg = { .rd = 1, .imm = a->imm };
    return trans_jal(ctx, &arg);
#else
    /* C.ADDIW */
    arg_addiw arg = { .rd = a->rd, .rs1 = a->rd, .imm = a->imm };
    return trans_addiw(ctx, &arg);
#endif
}

It parses RD manually, but not IMM :)  I'm actually going to eat now...